You and your cousin have the same grandparents. You didn't come from your cousin, and your cousin didn't come from you. Humans and chimpanzees are like that, only the "grandparent" lived about 6 to 8 million years ago.
No living species is the ancestor of another living species. Humans, chimpanzees and bonobos share an ancestor that lived roughly 6–8 million years ago. Old World monkeys like baboons and macaques split off from our line much earlier, about 25–30 million years ago. We are not descended from monkeys. We are apes, along with chimps, gorillas and orangutans.
1. The family tree
Read it from left to right, like a river that keeps splitting. Each fork is a common ancestor. The dates are approximate, and scientists argue about the exact numbers.
2. "Then why are there still monkeys?"
This question has the same mistake as asking "If Americans came from Europe, why are there still Europeans?" Populations split. One group changes one way, another group changes another way, and the ones left behind don't vanish.
Language works the same way. Spanish, French, Italian and Romanian all came from Latin. Nobody thinks Italian came from Spanish, and nobody is surprised that Spanish speakers still exist. Spanish and Italian are cousins, descended from a shared parent that no longer exists in that form. Apes and monkeys are the same: cousins that kept changing, each in its own way, for millions of years.
Also, both sides of a split change. Chimpanzees are not "what we used to be". They've had the same 6–8 million years to evolve that we had.
Why are there still monkeys if we evolved from them?
- Evolution is false
- We did not descend from today's monkeys; we share an ancestor with them
- Monkeys evolve slower than humans
4. The fossils
Hundreds of fossil individuals from at least a dozen species of early humans and their relatives have been found, mostly in Africa. Here are the best-known:
| Name | Age | Why it matters |
|---|---|---|
| Sahelanthropus (Chad) | about 7 million years | A skull with a mix of ape and human traits, near the time of the split. How "human" it was is still argued. |
| Ardipithecus "Ardi" (Ethiopia) | 4.4 million | A skeleton that climbed trees but could walk upright. |
| Australopithecus "Lucy" (Ethiopia) | 3.2 million | Found 1974. Her pelvis and knee show she walked upright, with a brain about the size of a chimp's. |
| Laetoli footprints (Tanzania) | 3.66 million | A trail of upright footprints left in volcanic ash. |
| Homo erectus "Turkana Boy" (Kenya) | 1.6 million | A nearly complete skeleton, tall and long-legged, a bigger brain. |
| Homo naledi (South Africa) | about 300,000 | A small-brained species that lived alongside early Homo sapiens. |
| Neanderthals (Europe, W. Asia) | 400,000 to about 40,000 | Their DNA survives in most people alive today outside Africa, about 1–2% of it.4 |
| Homo sapiens (Jebel Irhoud, Morocco) | about 300,000 | The oldest known members of our own species. |
Dates come from several independent methods (see dating methods), and the order of the fossils matches the order predicted from the DNA.
What does a shared ancestor predict about our DNA?
- Nothing in particular
- The closer the relative, the more DNA we share
- All animals share the same percent
5. "But weren't some of those fakes?"
One was: Piltdown Man, a forged skull announced in 1912. Scientists, not creationists, exposed it in 1953 using fluorine dating, and no research since has depended on it. A second famous mistake, "Nebraska Man", was a single tooth identified in 1922 and withdrawn by 1927, after it turned out to be a peccary's. Science can be fooled and then fixes the error. The real record doesn't rest on one skull: it's hundreds of fossils found by different teams in different countries, and thousands of genomes.
6. What would prove it wrong?
A good theory risks being wrong. Evolution would be in trouble if we found fossils of modern mammals in the Cambrian, if human DNA were no closer to chimps than to kangaroos, or if our genome had no matching leftover viruses. Researchers have looked for exactly this kind of problem for 160 years. J. B. S. Haldane's famous reply was "fossil rabbits in the Precambrian". None has turned up.
Many believers accept all of this. The Catholic Church has said evolution is compatible with faith, and scientists such as Francis Collins, who led the Human Genome Project, are Christians. For the claims that do conflict with the evidence, see where creationist arguments go wrong. For how life began in the first place, see where life came from.
7. Check it yourself
Sources
- Ijdo et al., "Origin of human chromosome 2: an ancestral telomere-telomere fusion", PNAS 88 (1991); Hillier et al., "Generation and annotation of the DNA sequences of human chromosomes 2 and 4", Nature 434 (2005).
- Ohta & Nishikimi, "Random nucleotide substitutions in primate nonfunctional gene for L-gulono-gamma-lactone oxidase", Biochimica et Biophysica Acta 1472 (1999); Drouin et al., "The genetics of vitamin C loss in vertebrates", Current Genomics 12 (2011).
- The Chimpanzee Sequencing and Analysis Consortium, "Initial sequence of the chimpanzee genome and comparison with the human genome", Nature 437 (2005); Lander et al., "Initial sequencing and analysis of the human genome", Nature 409 (2001).
- Green et al., "A draft sequence of the Neandertal genome", Science 328 (2010).